Part of the most difficult thing I've faced as a task in the conversion I'm doing is handing responsibility off to other people. Having done most of the desin work, planning, building control, four actions, block laying, timber frame arranging etc I reached a point where I was sick and tired of looking at heating systems (and I've made a couple of posts about it before) so I tasked he father in law with that. His brother develops high spec homes for people wih more money than sense and instantly jumped in with an ASHP recommendation so FIl starts looking into it

He's succeeded in getting a reasonable price out of a well known co who appear in all the magazines and trade shows for an ASHP, they've assured him the govt grant will cover it and he thinks it's the bollocks so he's sold..

I'm just still a little ambivalent; I worry about the noise it'll make, where is best to site it and keep refrigerant lines short (the roof?), whether the system as specified will suit having any complementary tech plugged into it in the future such as ST or PV, the Eco credentials if the COp falls below 3, the amount of hot water it'll produce (my missus likes to be warm, and having a new and growing family we use more hot water than ever) and ultimately, I'm spending twelve grand on a compressor to turn my house into a reverse fridge that faces the challenge of providing most heat when there is least available and most cooling when it's hardest to get rid of the waste heat, and it has a service life of 10 years

That 12k includes install of a 14kw Mitsubishi pump, 300 litre tank, and underfloor heating over 3 floors, and support from the co ongoing if there's a screwup somewhere and the performance is lacking. As to the fabric first, assume I can get somewhere near passivhaus levels of insulation and air tightness, 250sqm over 3 floors. As to what I need out of it- a set and forget system that won't cost an insane amount to run and will keep the missus warm and happy with plenty of hot water on tap. The bath she picked looks like it holds more water than the supplied cylinder :/

Ultimately, I suppose my query is "is it the right money (cos it looks like a lot of money) for the right solution for me?"
And if there are things (facts I haven't found out/provided) that prevent such a question being answered, what are they?

Thanks guys (and sorry to be a pain in the ass with many threads about heating.. It's just that the quote here for a heating system is more money than I spent putting a 2 bed bungalow shell up for my dad so it feels like quite a dent in the budget compared to an log boiler and tank, and spending the rest of e money on the fabric)

Posted By: cjardPart of the most difficult thing I've faced as a task in the conversion I'm doing is handing responsibility off to other people.

As to the fabric first, assume I can get somewhere near passivhaus levels of insulation and air tightness, 250sqm over 3 floors.

Yeah I found it difficult letting other people carry out aspects of my build, but in the end you have to 'cos you can't do everything yourself.

If you're going to be near PH then 14kW seems high, but then I don't know what part of the country you're in. I guess you don't have gas, I'd go for that first, if it was available. I would spend as much as I could on the fabric and have as simple a space and DHW heating system as possible. If you don't need much heat then even resistance electric is reasonable, possibly offset by PVs.

whats smart intergration of PV, direct connection.?
Id suggest PV an essential if installing any electrical heating device. do it intergrated into the roof to help balance cost (small saving on roof cover)
Actually Id like to say PV should be mandatory on all energy conscious new builds
PV immersion dump box with 4kW system will do a lot of your HW in the summer ( 4kW sys approx 5-6k cost)
12k for heating system for 250m2 sounds fine too (SE UK)
gas boiler and rad / tank install would up near that.
If no mains gas does LPG every make sense?
whats the tank / ufh cost £5-6k ?
id have thought looking for a cheap heating system you rarely have to use was the best route.

Sounds good , I'll do some research
First thought is I was under the impression HPs need long run time to get good COPs if heating HW via large surround blanket type heat exchange

<blockquote>I'm just still a little ambivalent; I worry about the noise it'll make..<blockquote>

The flue on my Oil boiler isn't exactly quiet. Perhaps louder than some ASHP?

Napier Uni did a fairly recent study of air pump outdoor units, which found that they were quite noisy, but the report was heavily criticised - their sample seemed to consist of about the oldest rickety units they could find!

Modern ones have sound pressures in the range 45-55. You should check your model, but even the latter is really acceptable. If you live in an area where there's any background noise at all, you shouldn't notice it. Remember they're the same things used for air conditioners in many hot countries and people really don't have a problem with noise.

On that, just to reiterate my problem with an ASHP system. With your well insulated build, I'd be gutted to spend £12k to heat your space (and water) with an SCOP of 3, when you could spend £2k on air to air units and heat the space with an SCOP of 4.

OK, so you still need to heat your water, but £10k is a lot to play with, either more solar PV or solar thermal or frankly an LPG or oil boiler - the extra efficiency of the space heating will offset the carbon emissions of your DHW system to an extent.

Shame you can't wait for R32 systems to become available. The extra 10% performance would be nice, and annoying to install something that will have a soon to be "obsolete" refrigerant.

http://www.topten.eu/english/building_components/air_conditioners/monosplit-5-6-kw.html&aid=513&adir=-1&direction=horizontal

This indicates 20% better, (SCOP of 5.5 vs. 4.6 for next best performing unit in Europe), which I just can't believe (I wish).

I -did- do more research, and found a Japanese study which suggested more like 10% in practise, but I can't find the link and don't have time to Google right now. It also explained the rationale for why R32 should perform better. It's all very persuasive. Basically, R32 was always known to be a bit better (and has a much lower GWP) but it wasn't used due to its flammability. Regulators have now decided that's not a worry.

While Daikin have been first off the mark in Europe (only mono-splits now, but they'll have an R32 multisplit available next year), other Japanese manufacturers (I think Fujitsu and Hitachi to name a couple) are already selling them in Japan, so presumeably won't be far behind. BUT, this all relates to A2A systems. Don't know about plans for A2W, but can't think why they wouldn't do the same for that.

Posted By: joe90Have you read jsh,s thread as indicated above by Triassic?, I think I remember him saying his ASHP was virtually inaudible.

Yes, but I seem to also recall that Jeremy's house is well designed, highly insulated and airtight, and his ASHP was working its bollocks off to produce 60 degree hot water, so he instead gets it to produce 40 degree hot water and uses inline resistance heaters on every hot outlet to raise the temp the final bit

Well, you can already buy this Daikin unit for £1,447, and you'd have the highest COP A2A unit on the UK market with a claimed SCOP and COP of 5.8. Output of 3.6kW, but up to 7.5kW, so should be plenty, although there are larger units.

If it performs as claimed, you would be heating your home at a 50% the cost of a high efficiency natural gas boiler, and with 60% less C02.

Even if it only manages 75% of stated performance (SCOP of 4.4), it would still be 32% cheaper than gas and 45% less CO2.

http://tinyurl.com/opg4eq4

If your house is well insulated and air tight, a single indoor unit centrally located might be all you need to heat the whole house. Multisplit not available until next year unfortunately.

A downside of the R32 unit is that you probably can't install them DIY as you can with R410A, since it's flammable, so you'd need to find an installer. Daikin UK should be able to advise.

You could always go for an R410A unit(s). They still achieve stated COPs in the high 4s, can be DIY installed, and they're cheaper since there's so many. This LG unit has an SCOP of 5.1, output of up to 6.8kW and costs £1065. The smaller ones are £910.

http://tinyurl.com/p72kpw2

How flammable, I wonder? I mean.. A pre teen is apparently competent enpugh to install Lynx deodorant ( in his nose, judging by some of the wackos I went to school with ) and that's pretty flammable.. So's petrol..

I shall definitely have a look though, as it might solve my desire for cooling too.

Might make the ufh install redundant though..


Am I right in thinking that I can't distrbute the heat round the house using the MVHR because it simply won't move enough air to carry enough heat to warm the place up ?

Why is an a2a cop higher than an a2w? Surely the process is more or less the same? Related to the output temp perhaps?f

Posted By: cjard
Why is an a2a cop higher than an a2w? Surely the process is more or less the same? Related to the output temp perhaps?f

A heat pump has a better COP if the dT is lower. The dT is the difference between the input T and output T. By going direct to air, rather then water, you can have a lower output T.

To heat the inside air to 20c, you need the water over 30c even with most UFH.

We discussed the issue of flammability a bit here. Technically it's classed as 'slightly flammable'. i.e. nowhere near as bad as the natural gas many of us get piped to our homes. There do seem to be other safety issues, to the installer rather than the householder, though I think. You probably could install it DIY as per R410A units, but, as with them, as I should have mentioned, your warranty wouldn't be valid then (need to be F Gas qualified).

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=13522&page=1#Item_0

Having compared with the highest performing R410A units (of which the LG one seems best), the extra 10% performance probably isn't worth the extra £400. In fact, I reckon you'd be best getting a couple of the smaller units, which I've found for £880 each, so just £1760, and have outputs of 6.6kW max, so 13.2kW altogether which would be loads for you.

Ringi's point is an interesting one. Means that this 'oversizing' might be useful. Unlike with A2W, A2A can modulate well and perform better when not working flat out. So oversizing will at least partially offset any loss of COP in cold weather (which would still be good). And of course, to your heat distrbution point, two units placed judiciously would help spread the heat better than one.

Finally, in addition to others' comments, I -think- the key to A2A's performing better is far greater simplicity. They're really such simple machines. They transfer heat from air to refrigerant and back to air again right where it's needed. A2W is from air to refrigerant, then an extra transfer to water, then that water transfers heat back to the air again in a way which seems far less efficient I think. If, with A2W, the heated water is stored in a tank, that's an extra source of losses.

Just reminded of this discussion from a comment on another forum. Results for both ASHPs and GSHPs really disappointing I think, particularly for the latter.

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=12769&page=1#Item_18